Conventional custom mouthguards are manufactured using a dental impression or replica of an individual's teeth, in particular the individual's upper teeth. The individual is provided with a tray filled with a modeling compound, which forms a negative impression when bitten. The negative impression may then be used to form a positive mold of the individual's teeth. Custom mouthguards have been created from the negative impression by vacuum forming or heat laminating generally thin polymer layers around the positive mold,